Heat-treated copper-nickel-aluminum alloy



Patented Apr. 22, 1930 UNITED STATES PATENT OFFICE WILLIAM A. MUDGE, OF HUNTINGTON, WEST VIRGINIA, ASSIGNOR, BY MESNE AS- I SIGMENTS, .TO THE INTERNATIONAL NICKEL COMPANY, INC., OF, NEW YORK,

N. Y., A CORPORATION OF DELAWARE HEAT-TREATED COPPER-NICKEL-ALUIMINUM ALLOY No Drawing. Original application filed March'31, 1925, Serial No. 19,730. Divided and this application filed July 13, 1925.

My invent-ion relates to the treatment of alloys containing as their main ingredlents nickel, copper and aluminum, wherein the aluminum is from about .1% to 17%. (from about 2% to 7% preferred) the copper is 10 small amounts of other elements, such as iron,

following discoveries:

manganese, carbon, etc. The manganese may increase somewhat, thus, of course, correspondingly decreasing slightly the proportions of the main alloying elements.

I have discovered that an alloy of the above nature may be materially changed and improved in physical properties by proper heat treatment. While the exact physical and chemical reasons underlying this phenomenon are not known to me at present, I believe that the change in physical properties isprobably due to the formation by such treatment of a compound of copper and aluminum or possibly a compound of nickel, copper and aluminum. Apparently the amount of such compound or compounds formed vary with the different compositions and the heat treatment and may account for the variations noted in. the physical properties. i

In a long series of experiments on heat treatment of this material, I have made the If the material has been quenched from a temperature of 1500 F. and above, it will be dead soft. If such dead soft material. is heated, I have found the following facts:

(a) Up to about 600 F., there will be practically no change in the physical properties.

(6) Between 600 F. and 1000 F., a. gradual increase in desirable physical properties and hardness will result.

(a) At a range from 1000 F. to 1200 F., the maximum desired properties will be developed.

By physical properties in the above statement, I mean that the proportional limit, yield point, and ultimate strength and hardness will be increased, while the elongation and reduction of area will be decreased.

Serial No. 43,403.

The above statements apply regardless of the rate of cooling, but slow cooling from any of the temperatures above mentioned will, in general, give better physical properties than when the material is rapidly cooled from these sametemperatures, as for example, by quenching in oil or water or in any other suitable quenching medium.

If the material is heated to a temperature above 1200 F., there will be a decrease in these physical properties, and this decrease will be proportional to the increase in temperature from 1200 F. up to below 1800 F.

Also the rate of cooling will effect the desired physical properties in this case. When rapidly cooled or quenched, the desired properties will be slightly lower than when slowly cooled from the same temperatures.

Also, there is a time effect in the heating, since extending the time'of heating tends to increase the desired physical properties. For example, using dead soft material and one hours heating at the best temperature of about 1100 F. would give semi-hard material, whether cooled slowly or rapidly; whereas if this heating at this same temperature on the same material was continued for eight or more hours, a hard material will be produced having physical properties considerably in excess of those produced in one hours heat treatment; and this again, whether the cooling is rapid or slow.

Continued heating at the maximum temperature of about 1100 F. for more than eight hours will slightly, but definitely, increase the physical properties regardless of the rate of cooling.

As a specific illustration of these treatments, I will recite the following example, the material treated being composed of about 45% of nickel, 55% of copper and 4% of aluminum, together with 1.02.5% of iron and manganese and 05-25% carbon as commercial constituents.

First emample.0riginal material whose proportional limit was 80,000 psi. was quenchedafter heating for one hour at 1500 F., which reduced its value to 30,000 psi. Heating at 1100 F. increased the proportional limit from 30,000 psi. to 80,000 psi. at

the end of three hours. The proportional limit was further raised to 95,000 psi. at the end of the fifth hour. Longer heating at 1500 F. or an equal period at 1750 F., when followed by quenching, will reduce the proportional limit of the original material to 20,000 psi. In this event, a longer heating period at 1100 F. will be required to increase the proportional limit to 95,000 psi. In this case, all the heating was carried out at 100 F. and followed by slow cooling in air, but similar results might have been accomplished by rapid cooling following the same heat treatment.

It will be noted from this example that starting with an original material of high physical properties, the heat treatment reduces these physical properties to a minimum and then raises them beyond the original values, all by heat treatment and without mechanical working.

Second emampZe.-When this alloy has been hardened and the desired physical properties developed to a high value by the heat treatment, such as before described, it may be heated in the following ways without affecting its properties:

(a) To any temperature not to exceed 1200 F. with slow cooling.

(1)) To any temperature not exceeding 1100 F. with quenching or quick cooling.

This discovery is important, especially in using the material in locations where it is subjected to variations in temperatureconditions, as for example, when used for steam turbine blades. The maximum temperature in turbine work is lower than the above points, and hence, the material will retain its desired physical properties under these conditions, even under Wide variations of temperature. .In other words, intermittent service at or below these temperatures does not materially change the characteristics of the material, if tested when cooled down.

If the material is heated above these temperatures, a decrease in the desired physical properties will result, without regard to the rate of cooling, but if the material is slowly cooled after such heating, it will have higher properties than if quenched after heating to above such temperatures.

Third ewampZe.If'this hardened material is heated to a point between 1200 and 1500 F., a semi-hard material will be produced,

- regardless of the rate of cooling, although the slowly cooled material in this case will be slightly harder than the quenched or rapidly cooled material. If this hardened material is heated to above 1500 F. and quenched or rapidly cooled, it will produce dead soft material; while slowly cooling it from a. temperature of 1500 F. or above will produce a semi-hard material.

Using the same methods of heat treatment described in the examples noted above, the

proportional limit of an alloy containing 90% nickel, 5% copper and 4.5% of aluminum has been varied between 20,000 psi. and 03,000 psi. The same heat treatment permits a variation with an alloy containing 85% nickel, 10% copper and 4% aluminum of 20,000 psi. to 85,000 psi. The same heat treatment again permits a Variation with an alloy containing nickel, 25% copper and 4% aluminum of 25,000 psi. to 105,000

I have found that the optimum hardening temperature is about 1100 F., when followed by slow cooling in air, apparently regardless of the specific chemical composition of the alloy.

The above examples recite the major discoveries which I have made in my heat treatment research on such alloys. I will now describe certain other features which I have found in this research.

Either the dead soft or semi-hard alloy, when these properties have been imparted by the proper heat treatments, can be machined or fabricated with about the same ease as a similar nickel-copper alloy containing no aluminum.

If the material is hardened and has the desired physical properties to a high degree, it is machined with considerable difliculty. Therefore, any one machining or fabricating this material while relatively cold and without material heating, to obtain a certain article or device,- would probably desire it in soft or semi-hard condition for such treatment; and thereafter, the desired physical properties can be imparted by heating at from 1000 to 1200 F., the properties increasing with the length of heating, as above described, and being preferably followed by a slow cooling to bring these properties to their highest value.

Where the material is worked in hot condition for sale in merchant shapes, the best rial as rolled or otherwise hot worked should be quenched or quickly cooled from a temperature of 1500 F. to give a soft material.

If, on the other hand, there is desired a very hard alloy possessing the desired physical properties to a high degree, the best practice is to allow the material to cool slowly after hot working at the above temperature and then heat the material at from 1000 to 1200 F., for several hours and allow it to cool slowly in the air. As above pointed out, the longer this heating extends within certain limits, the more" of'the compound will be formed and the greater the physical characteristics.

While I'do not know definitely the chemical or physical reasons underlying the phe- I nomena, it seems reasonable to suppose that the hardness and other desired physical properties may be due to the gradual formation of a copper-aluminum compound or possibly a nickel-copper-aluminum compound during the heating.

I have also found that where the desired properties are imparted, either to a high degree or to a medium degree, these properties are slightly improved by aging of the material. Thus, where the material had been quenched from 1500 F. and above, to produce dead soft material, the proportional limit being reduced from 80,000 psi. to 25,000 psi.,

this material was heatedat about 1100 F. for one to three hours, and some samples quenched and others slowly cooled.

In both'cases, one sample was tested about five minutes afterv cooling and another about twelve weeks after cooling. The aged samples from both the quenching and the slow cooling were found to be improved in proportional limit and hardness by from 5 to 15%.

My improved heat treatment is, of course, applicable to a nickel-co per-aluminum alloy containing .1 to 17 0 aluminum, whether in the cast condition or when worked hot or cold or machined.

This application is a division of my copending application Serial No. 19,730, filed March 31,1925, for manufacture of alloys of copper, nickel and aluminum.

In the present case, I intend to cover broad- 35 ly the method above described wherein rapid cooling is used, as for exam 1e, by quenching, and in the more speci 0 claims rapid cooling from a temperature of over 1000 F. I also intend to cover the article produced thereby.

The advantages of my invention result from the physical characteristics obtained by rapid cooling, which characteristics may be varied according to the temperature from whichthe rapid cooling is applied. In the preferred form, where the material is rapidly cooled from a temperature of 1500 F. and upward, dead soft material is provided which can be easily machined and worked. Smaller percentages of other metals or metalloids may be used or not as desired, and other variations may be made without departing from my invention.

I claim: 1

1. In the treatment of nickel-copperaluminum alloys containing from 2% to not over 17% of aluminum and at least 15% of nickel, the step consisting of softening the material by rapidly cooling it from a heated condition short of its melting point, such conditions being sufficient to soften the ma terial when cooled.

2. In the treatment of nickel-copperaluminum alloys containing from 2% to not 65 over 17% of aluminum an at least 15% of nickel, the step consisting of softening the material by rapidly and artificially cooling it from a heated condition short of its melting point, such conditions being sufficient to soften the material when cooled.

r 3. In the treatment of nickel-copperaluminum alloys containing from 2% to not over 17% of aluminum and at least 15% of nickel, the step of softening the material by.

rapidly cooling it from a temperature of over 1000 F. but short of its melting point.

4. In the treatment of nickel-copperaluminum alloys containing-from 2% to not over 17 of aluminum and at least 15% of nickel, the step of softening the material by over 17 of aluminum and at least 15% of nickel, the steps consisting of heating-the material to 1500.F. or over, but short of melting, and rapidly and ing it.

7. As a new article of manufacture, a relatively soft, easily machined alloy of nickel, copper and aluminum containlng from 2% to not over 17 of alumlnum and at least 15% of nicked and having a physlcal structure such as is produced by treating an alloy of this composition by quick cooling from a temperature of 1500? F. or above.

'8. As a new article of manufacture, a relatively soft, easily machined alloy of nickel, copper and aluminum contalnlng from 2% to not over 17 of aluminum and at least 15% of nickel and havlng a phys cal structure such as is produced by treatrng an alloy of this compositlon by quick cooling from a temperature of 1500 or above, and having a proportional limit of 20,000 'to 40,000 psi. v

9. In the treatment ,of mckel-copperaluminum alloy containing less than 20% of aluminum and at least 15% of nickel, the

steps consisting of heating the material to above 1500 F. and quickly cool ng.

'10. In the treatment of nickel-copper aluminum alloy containing less than 20% of aluminum and at least 15% of nickel, the steps consisting of softening the material by rapidly cooling it from a heated condition, the temperature being sufiicient to soften the material when rapidly cooled.

11. In the treatment of nickel-copperaluminum alloy containing less than 20% of aluminum and at least 15% of nickel, the

artificially cooli iso steps consisting of heating the material and subjecting it to quick cooling action to change the physical properties, the temperature being sufficient to soften the material When quickly cooled.

In testimony whereof I have hereunto set my hand.

WILLIAM A. MUDGE. 

